Presently known balanced mixer devices require two separate diodes for their operation. Typically such diodes comprise Schottky barrier diodes where operation is required in the millimeter wave frequency range. Due to the requirement of two such diodes, the fabrication of monolithic type signal mixer circuits becomes relatively complex in their construction.
On Oct. 18, 1983, one of the present inventors, Roger J. Malik, was granted a patent, U.S. Pat. No. 4,410,902, for a "Planar Doped Barrier Semiconductor Device", which is comprised of an n.sup.+ -i-p.sup.+ -i-n.sup.+ semiconductor diode structure wherein an extremely narrow p.sup.+ planar doped region is positioned in adjoining regions of nominally undoped (intrinsic) semiconductor material and is fabricated in accordance with a known process called "Molecular Beam Epitaxy" wherein the device is grown on a semiconductor substrate such as gallium arsenide. By varying the acceptor charge density and the undoped region widths, low barrier heights can be obtained and can be used to replace Schottky barrier devices which exhibit relatively large barrier heights and thus reduce the power requirements for the application intended.
Accordingly, it is an object of the present invention to provide a means for mixing an input signal with a local oscillator signal to provide an intermediate frequency output signal.
It is another object of the present invention to provide a signal mixer which operates in the millimeter wave frequency band.
Still another object of the invention is to provide a signal mixer fabricated as a monolithic integrated circuit structure.